Multilayered structural insulated panel

ABSTRACT

A structural insulated panel includes an internal foam (EPS) core, oriented strand board (OSB) faces on the core, and a sheet of magnesium oxide (MagOx) on one or both of the faces for environmental purposes of either weather resistance and/or fire protection. The outer faces incorporate interior and exterior surfaces that need little more than a finish top coat paint. The combination of core, oriented strand board, and outer sheets provide a thermally efficient insulating structure that is a fully nationally code approved building structure.

This application claims benefit under 35 U.S.C. §119(e) of provisionalapplication Ser. No. 61/075,054, filed Jun. 24, 2008, entitledMULTILAYERED STRUCTURAL INSULATED PANEL, the entire contents of whichare incorporated herein in its entirety.

BACKGROUND

The present invention relates to structural insulated panels useable inbuildings.

The building industry continues to be challenged by increasing costs ofconstruction, including material and labor. Large structural insulatedpanels (e.g., 8 foot×24 foot panels) can help by reducing the number ofcomponents and pieces that must be handled during construction, andfurther by reducing energy costs in the buildings once constructed.However, further improvements are desired to reduce on-site work andreduce components costs, and to reduce the risk of poorassembly/construction. For example, insulating systems are known for usewith studded wall constructions (e.g., fiberglass batting, cellulose,and/or sprayed urethane products), however these systems are prone tohave gaps that allow drafts and/or they can be squeezed thin such thatthey do not provide the insulative “R” value advertised.

In particular, it has been challenging to make structural insulatedpanels (SIPs) that meet cost, weight, code, environmental and structuralrequirements. Oriented strand board (OSB) by itself can potentially meetcost, structural and weight requirements, but it does not meetenvironmental needs for weather or code requirements for fire unless itis further covered or treated. Structural products made of foam areadvantageous since they have low weight, but foam by itself potentiallylacks strength. Further, when a fire occurs in a room lined with barefoam, the room heats up very quickly to a point where the foam mayexplode in flames. Because of this, residential building codes requirethat the plastic foam be separated from the inside of an enclosed areawith the equivalent of ½ inch drywall. Notably, it is not acceptable tosimply construct a structural insulated panel using a foam core coveredwith oriented strand board, since fire codes are not met. Further,substantial secondary finishing and/or covering layers must be added.However, available materials might include cementous materials orintermessent paints that, when they are machined in the factory or latercut in the paint, produce fine particles of silicon dust which are ahealth hazard (silicosis) or are destructive to cutting machines.

SUMMARY OF THE PRESENT INVENTION

In one aspect of the present invention, a structural insulated panelincludes an internal foam (EPS) core, oriented strand board (OSB) facesof the core, and at least one thin sheet of non-cementous, fireretardant material (such as magnesium oxide (MagOx)), on one of thefaces.

In narrower aspects, magnesium oxide sheet is attached to one or both ofthe faces with an adhesive.

In another aspect of the present invention, a method comprises steps ofproviding a foam core with oriented strand board faces, and applying athin layer of magnesium oxide sheet over the faces.

In another aspect of the present invention, a structural insulated panelincludes a structural insulated panel (SIP), and at least one thin layerof fire retardant material such as magnesium oxide (MagOx) on at leastone of the faces of the structural insulated panel.

An object of the present invention is to provide an improved structuralinsulated panel that is energy efficient and insulative (e.g., 50% moreenergy efficient over conventional “stick” wood-stud-builtconstruction), goes up quickly, and incorporates interior and exteriorsurfaces that need little more than a finish top coat paint . . . andwhich are fully nationally code-approved structures.

An object of the present invention is to provide an improved structuralinsulated panel of large size (e.g. 8 feet×24 feet), and which can becustom cut (e.g., by using CNC-type equipment) to match a building plan.

An object of the present invention is to provide a large panel having ahighly insulative value and hence excellent energy efficiency, butcompetitive price when compared to other products (including theirrequired on-site construction work such as the cost and labor andsecondary processes required when using studs).

An object and function of this invention is to provide a light, smooth,thin layer of material over the OSB that will meet the fire coderequirements and interior surface finish requirements.

An object and function of the present invention is to provide layeringof a smooth layer of fire resistant material over the OSB that allowsthe SIP panels to meet the common code requirements for a thermalbarrier or over the foam core of the SIP.

These and other aspects, objects, and features of the present inventionwill be understood and appreciated by those skilled in the art uponstudying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a multilayered panel of the presentconstruction.

FIG. 2 is an enlarged transverse cross section through FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A structural insulated panel 20 (SIP) (FIGS. 1-2) includes an internalfoam (EPS) core 21, moisture-resistant oriented strand board (OSB) faces22 on the core 21, and thin outer sheets 23 of non-cementous, fireretardant material, such as magnesium oxide (MagOx) adhered to theexposed faces of the oriented strand board. The thicknesses and sizescan be varied as necessary (see FIGS. 1-2) for particular building coderequirements and particular builder preferences. By making the sheets 8feet×24 feet, building efficiencies can be achieved that were notpreviously possible using structural insulated panels. Further, it iscontemplated that the large panels of 8 feet×24 feet can be cut to matchcustomer plans by using CNC machines, such as by cutting door, window,and outlet openings into the large panels.

In ASTM E84 fire testing, it takes about 15 minutes for the back side ofdrywall to raise in temperature from ambient to above 250 degreesFahrenheit. I refer to this as the “15 minute rule” for thermal barrier.

I have found that magnesium oxide sheet can be advantageously applied toexposed surfaces of oriented strand board adhered to the inner and outerfaces of a foam core in order to pass the “15 minute rule” for thermalbarrier of a building wall. More specifically, the magnesium oxidesheets as a face permit the arrangement to meet the environmentalrequirements for a building wall for weather and code requirements forfire. I have found that since magnesium oxide does not burn, it keepsenough heat off of the wood oriented strand board so that the laminararrangement meets the 15 minute thermal test. An optimal approximatethickness of the oriented strand board is about 7/16 inch and themagnesium is about 2 mm. However, it is contemplated that a scope of thepresent inventive concept includes a internal foam (EPS) core that is atleast about 3½ inches thick up to several inches thick, and the orientedstrand board (OSB) faces can be about ½ inch to 1 inch thick, and the atleast one sheet of magnesium oxide (MagOx) can be about 5 mm thick, ormore preferably about 3 mm thick.

14.

Notably, thin magnesium oxide sheets only come in 4 foot×8 foot sheetsizes. However, using the present inventive concepts, thin magnesiumoxide sheets can be readily used to make big panels, such as 8 feet×24feet, by applying 4 foot×8 foot sheets of magnesium oxide to the bigoriented strand board. This is a significant advantage for builders,since it makes for a more efficient and quicker building construction.It also has advantages since, by doing this at a factory, tightertolerances and joints can be made. It is noted that the smaller 4′ widepanels of magnesium oxide would take much longer to install individuallyat a construction site, and also would be much less structural than whenthey are integrally bonded to form part of a larger 8 foot×24 footlaminar arrangement. Further, separately attached 4 foot×8 footmagnesium oxide sheets would result in more junctions and hence more airinfiltration to a building . . . as well as more “crease” locations (ifnot tightly abutted at joints) potentially resulting in hot spots thatpermit fire intrusion. For this reason, in my opinion it has beencounterintuitive to make the presently-proposed laminar arrangement.This explains, at least in part, why it has not previously been done.

In addition to using the present arrangement on an inside wall surface,the exterior wall surface gains advantages using magnesium oxide over“bare” oriented strand board. Here, the magnesium oxide can act as aweather resistant surface. Also, in areas where fire is likely to occuron the outside, the magnesium oxide provides an “external” resistance tofire that is desirable. The fire resistance can also be provided incellulose or other materials by impregnating it with ammonium phosphateor with phenolic or with another fire retardant material, or byincluding in a paint or adhesive a fire resistant material.

It is noted that national codes approve panels made with oriented strandboard faces on foam. This makes passing of fire testing a keyrequirement for product sales to the housing and building industry.Hence, the present invention is highly advantageous and very importantfor product sales to the housing and building industry for structuralinsulated panels.

It is to be understood that variations and modifications can be made onthe aforementioned structure without departing from the concepts of thepresent invention, and further it is to be understood that such conceptsare intended to be covered by the following claims unless these claimsby their language expressly state otherwise.

1. A structural insulated panel (SIP) comprising: an internal foam (EPS)core, oriented strand board (OSB) structural faces on the core, and atleast one sheet of non-cementous, fire retardant material on one of thefaces.
 2. The panel defined in claim 1, wherein the at least one sheetof fire retardant material is attached to the oriented strand board withan adhesive that adds to the fire retardancy of the facing.
 3. The paneldefined in claim 2, wherein the at least one sheet of fire retardantmaterial is on the inside only.
 4. The panel defined in claim 1, wherethe sheet is made of magnesium oxide, gypsum composite, celluloseimpregnated with ammonium phosphate or with amnonimun phosphate, orcellulose impregnated with phenolic.
 5. The panel defined in claim 2,wherein the at least one sheet of fire retardant material is on theinside and outside faces.
 6. The panel defined in claim 5, wherein eachof the core, structural faces and at least one sheet add to thestructural integrity of the panel.
 7. The panel defined in claim 5,wherein the panel is at least about 8 feet by 24 feet.
 8. The paneldefined in claim 1, wherein the at least one sheet of fire retardantmaterial includes sheets on the inside and outside faces.
 9. The paneldefined in claim 1, wherein the panel is at least about 8 feet by 24feet.
 10. The panel defined in claim 1, wherein the internal foam (EPS)core is at least about 3½ inches thick, and the oriented strand board(OSB) faces are about ⅜ inch to 1 inch thick, and the at least one sheetof fire retardant material is at most about 5 mm thick.
 11. The paneldefined in claim 10, wherein the oriented strand board (OSB) faces areabout ⅜ inch to ¾ inch thick, and the at least one fire retardant sheetis at most about 3 mm thick.
 12. A method comprising steps of: providinga foam core with oriented strand board faces; and applying a thin layerof fire retardant sheet over the faces.
 13. A structural insulated panelcomprising: a structural insulated panel (SIP); and at least one thinlayer of fire retardant material on at least one of the faces of thestructural insulated panel.